Hear Our MP3... Win an X-Box?
Here's an interesting idea. A band is running a sweepstakes, an X-Box is the grand prize, and the winner will be chosen from everyone who registers to listen to an MP3 of their song.
Though a stunt like this might not gain you many new core audience members, you certainly can increase the number of listeners who sample your track. And that's always a good thing. While the idea is still novel, you could also benefit from a little publicity (like these guys are now).
Not the first play I'd pull from the playbook, but I have seen folks do far worse things with a few hundred dollars.